I've seen a few sites of some folks building their own out of acrylic but I'd have to search again to find them. There has been quite a few people who have made overflows just out of pvc pipe that also work. Personally, I was going to go the overflow route before with my tank but then decided to drill it instead. Drilling is way more reliable and there's less of a chance of flooding a tank or sump when properly set up. You can do a search on u-tube for diy overflows and should pull up several videos.
The plumbing is really going to depend on which way you want to go. You can hard plumb or use flex pipe, it's all a matter of personal choice. If there are going to be a lot of bends then flex pipe is good in illiminating alot of that resistance. On my build I'm going to hard plumb my drain lines and they will just drop right into the sump. And on my return line I will use flex pipe connected from my return pump up to my return fittings in the tank that are connected via a bulkhead that I install in the tank, also through drilling. But you could also just pick up a return tube that hangs over the back of the tank that connects to the return line.
